I use the needles for mulch, for my own containers I use diatomaceous earth. The Napa product or Optisorb. Both 100% DE used as oil absorbers. Cheaper than perlite. Much better than perlite as they hold water. I have a problem with drying soils in the summer, so they stay moist longer but allow great aeration also. They never breakdown either. Perlite does in about 5 years. I buy my own ingredients for potting soil. Pine bark fines ( a local nursery sells them as soil conditioner), peat moss, compost, and DE. Plus maybe lime or gypsum depending what I want to grow in it. A little organic and time release fertilizer, and small amounts of rock phosphate or other mineral supplements.
Doesn't hay have a ton of seeds? Not the best additive. I use straw for mulch. Here since Halloween has passed I collect the small bales people use for decoration, I trash hunt for it. I also got about 50 pots so far that are perfectly fine people have thrown out.
By the time I'm done adding things, I have to take a 2nd job to pay for it! So maybe use hay
No manure around here except the dog's, not really good to use! I sometimes put it in the ornamental flower bed, but not with edibles! No compost pile here in the middle of suburbia, no room, looks like crap, the wife would kill me.